Slow Cooker Hot Process Soap Recipe

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This Slow CookerHot Process Soap Recipe is a good first-timer soap recipe choice. The advantage of hot process recipes are that the bars are ready almost immediately, rather than having to wait the month or more before you could use Cold Process soap.

Why Make Soap?

Have you ever wanted to make your own soap? I love making my own soap several times a year. The reasons I make my own soap:

After I started to use homemade soap, every other soap seemed so artificially-fragranced and I came to dislike how the fake scent from the lab-produced fragrance oil lingered uncomfortably on my skin

Homemade soap has become my favorite small gift, either by itself or as part of a gift basket; people really seem to appreciate it and are amazed that you made it yourself

I love watching the ingredients come together and turn into something special. It’s chemistry, but it seems like magic

I love customizing base oils and essential oils to make special-purpose soaps

I love how homemade soap smells, even before I add essential oils

It’s really fun!

Making soap can seem very intimidating at first, but it really is doable once you have the right equipment and follow some simple safety rules.

Simple Soap Safety In a Nutshell:

Dress in old, long-sleeved, leg-covering clothes and perhaps an old apron to cover your skin and protect you from splatters

Use rubber gloves

Wear safety glasses

Maintain good ventilation (your stovetop vent hood, a small fan, or an open window is good)

Keep small children and pets out of the area while soaping

Set up your equipment and supplies before you start and read all instructions before you begin

Get your equipment ready

Hot Process Soap Recipe

36 oz. olive oil (emollient and gentle)

6 oz. coconut oil (helps make a good hard bar)

3 oz. castor oil (improves suds)

6 oz. lye

12 oz. water (I use 100% sodium hydroxide drain cleaner granules from the hardware store or I buy it online)

2-4 oz. essential oil of choice, optional

For the Honey and Oatmeal version, add 3 Tablespoons of honey as soon as the soap has passed the zap test (at the point when you would be adding the essential oils). Turn off the crock pot and stir in a mixture of 3 Tablespoons of oatf lour and 3 Tablespoons water. Stir well and mold as usual.

Equipment:

scale (Digital is nice but not essential; check overstock stores for deals.)

immersion/stick blender

crock pot/slow cooker (I got mine at Goodwill on the cheap to use exclusively for soap-making.)

large non-aluminum bowl or pitcher (Hard plastic is fine.)

long-handled plastic spoon

old newspaper

soap mold (or an empty Pringles can, a washed milk carton, or special soap molds from the craft and hobby store.)

If you can’t find these secondhand, try these alternatives I selected for a balance of good reviews and low cost:

Prepare Your Ingredients:

Turn heat on low and allow to melt if necessary (coconut is solid above ~70 deg.)

Measure water and pour into pitcher or non-aluminum bowl.

Weigh the lye.

Time to Combine

Add lye to water and stir gently to dissolve (l like to set the bowl in the sink before I add the lye and do my pouring and mixing in the sink)

REMEMBER: Always pour the lye into the water, not the other way around or you can have a volcano. Mnemonic device–remember ‘snow falling on a lake’ is the right way. Don’t stick your head over the lye mixture during or after the add–avert your face because it can gives off fumes

Allow the lye water to cool for a few minutes so it’s not super hot; combining the lye and water produces heat. (This isn’t the hot part of the hot process soap recipe! Even cold process soaps have this part.)

Then pour the lye water into the oils in the crock pot and give it a gentle stir.

Grab your Blender

The immersion blender goes carefully into the lye water+oil

Plug in your immersion blender and lower it to the bottom of the crock pot into the oil mixture. Hold the blender at a slight angle so it doesn’t suck itself to the bottom of the pot, but also make sure it is fully immersed in the solution to minimize splatter.

slowly rotate the blender around the bottom of the pot until it reaches trace

Turn on the blender and gently stir.

a pretty thick trace–it doesn’t have to get this thick to be ready

Keep stirring until you reach the slightly mysterious point known as “trace.” All that means is the mixture will be pudding-y enough so that stirring leaves a faint trail as you move the blender or a spoon through the mixture.

Cover and wait

Remove the immersion blender, unplug it, rinse it, and set it aside.

Slow Cooking

Put the lid on the slow cooker and let it heat up on low. (This is the “hot” part of the hot process soap recipe.)

Warm until the sides begin to pull away and it starts to look like something interesting is happening.

see the darker part underneath?

This will take several minutes depending on the volume of your oils and the heat of your crock pot.

the sides begin to change

Using your spoon, stir the mixture down, scraping the bottom and sides.

Allow to cook for an additional 20 minutes or so (times can be inexact), stirring frequently at the beginning and constantly toward the end of the cook.

completely bubbled top

Don’t leave your soap.

the texture has transformed completely

It will begin to start to look like applesauce and become a bit waxy-looking.

Continue stirring until it begins to darken and become more opaque and waxy.

Keep cooking and stirring. It may “rise” and “fall” again as it completes the saponification (turning into soap) process.

How to know when it’s done: I let a tiny dab of the soap cool on the end of my spoon and touch it with the tip of my tongue to see if the soap “zaps” like a 9-volt battery. If it doesn’t zap, it’s ready to put into the molds. If it zaps, it needs to cook some more.

stir it in quickly before it begins to cool!

Molding and Cooling

Once it is zap-free, quickly stir in your essentials oil(s) and spoon the soap into the mold or molds. It may look quite amber at this point; it will lighten up as it cools.

smooth it out quickly because it hardens fast

After several hours or overnight, the soap should be cool throughout and hard enough.

Remove from the mold and slice.

slice it as thick or as thin as you prefer

Technically the soap at this point is ready to be used, but it will improve and harden with a couple of weeks curing time.

the ways to package soap are unlimited

After it’s cured, package it up and keep it on hand for gift-giving and your own use. I like to print out labels I make up with the type of soap and ingredients. The sky’s the limit in terms of presentation. Simple craft paper, paper bags, cellophane treat bags, baker’s twine, sisal, ribbon or fabric make great soap adornment.

You can use any soap recipe for hot process soap, including recipes for cold process soap. However, I’d stay away from recipes that call for lots of additions like dairy or texture, especially at first. Hot process is hot and those things can increase the likelihood of scorched soap.

Here’s one of my favorite soap recipes, one I included in our book, which, incidentally, has a great section (if I say so myself) on soap-making and four of our favorite recipes for soap, as well as lots of other homemade goodies that go great in a gift basket with soap.

Hi Al–You can make crockpot soap with bacon fat. Clean the drippings as described in the bacon soap post and use the crockpot method using the resulting fat as your oil. You can also combine the bacon/drippings fat with other oils if you like. Use a lye calculator like this one: http://www.thesage.com/calcs/lyecalc2.php and plug in your weights to get the amount of water and lye you will need. If you are just starting to make soap, I recommend using a recipe that doesn’t have add-ins such as oatmeal and which use milk. Add-ins is an issue you can battle after you have a couple unqualified successes under your belt.
I’m not sure I’ve answered your question, so please let me know if I’ve just been confusing. Good luck!

You answered my question. Thank you. Yes I’m a beginner and am wanting to make my first batch soon. At some point I would even like to make my own lye (scary!). Oh, and thanks for the link too… I’m finding it hard to find ratios and recepies. Most tutorials are for “those who are familiar with soap making”. I need all the help I can get! lol.

Ooops! Another question lol! I was just sitting and making a list of things I need for my first batch. Now, I was wondering, do the essential oils count as add ins? Should I make my first batch unscented just to keep it simple?

Made my first batch of HP soap today, not sure if it will turn out-that is how I ran into your website. The soap did look like your pics. I thought there was way too much oil separating from the soap so I kept turning the crock pot on and off 15-20 min at a time for about an hour. The final result resembled vaseline when I poured it. I also noted some liquid at the bottom of the crock while I was pouring it. Guess I’ll find out in the morning if it will turn out.

Thank you for the excellent tutorial and the links for the molds and guillotine!!! My sweety took the picture out to the shop and came back with a mold and a guillotine, so I was prepared. I am hooked on crockpot soaping!! I made my first batch on Monday. It just all came together so easy! It cooked for 1/2 hour — I was expecting more. Glopped it out (very nice mashed potatoes), unmolded the next morning and sliced. 17 bars of wonderful soap!!

However, I made another batch last night. This time I used goat’s milk for the water. Hmmm, after 4 hours of cooking, I had to go to bed (12:15 a.m. at this point)!!!!! It’s still tingy to the tongue. I have to go out of town for today, so I’m hoping I can chunk up and rebatch when I get home. I’ll try it, it can’t hurt!

I have done this recipe when you first posted this and loved the ease and quickness of it. My question is how to get more lather. I read somewhere to put sugar in. Would you put it in with the oils or with the oat flour? I love your blog. I have gained a lot of info from you, thank you so much for all you do.

Hi. I have a few questions and a comment. I’ll start with the comment. Adding castor oil to your mix will make nice suds.

Now the questions: Can you use any recipe for hot process that you do for cold process? And does anyone have a basic recipe for a milk soap using lard only? All I have to get online with is my phone and it won’t run the soap calculator right. Thank you.

Deb–I believe, in theory, cp and hp recipes are similar proportions. You may choose, especially in the beginning, to use some “tried and true” hp recipes while you are becoming comfortable with it, i.e., recipes that go along with particular tutorials, especially as they are often designed around certain batch sizes for, say, X-capacity crock pots or certain size pans for oven or direct heat or double boilers.

I found this recipe: http://www.homesteadingtoday.com/showthread.php?t=282258, authored by “Wendy,” (props to Wendy : ) ) and ran it through the mms lye calculator. In the “green” range (5%-8% excess fat range–the recommended range) the lye suggested is from 9.12 to 8.83 oz., so the recipe’s 8.5 oz. lye is nicely within that range. The liquid suggested for those oils (1 # coconut and 3 # lard) is 16-24 oz. also within the recipe’s 24 oz. goat milk. So, sounds like a winner. If you want to use all lard for that same size batch, i.e. 64 oz. lard, the lye calculator for the green range suggests from 8.43-8.17 oz. lye and again, 16-24 oz. liquid.

Thank you so much. I forgot to mention that my crock pot comfortably makes a batch of soap using 32oz. of fat, and my mold is a 2 lb. mold. I use a basic soap recipe that calls for 30oz. lard, 2oz. castor oil, 10oz. water, and 4.5oz. lye. It makes great soap, and takes fragrances well. I don’t use dyes. Do I just divide the recipe that you gave me, or will it need to be recalculated? Thank you.

Good morning! Thank you for taking the time to do this. I want to do the 30 oz. lard and 2 oz. castor oil recipe. Coconut oil is too pricey for me right now.

I have customers requesting milk soap, so the other day, I tried to make milk and honey soap, but I think I scorched the milk. (I didn’t freeze it.) But I did sit it the container I mixed the lye into it with down in a bowl of ice. It turned brown and curdled. I added it to my oils anyway, and it smelled just awful. Then, at trace, I added the honey. it started turning a really neat orange color, then it just got darker and darker, and smelled so AWFUL! I had to pitch it. YUCK

Deb–The lye calc says: 8-12 oz. liquid, 4.20-4.07 oz. lye (within the green range).
As for the milk, everything I’ve ever read says freezing the milk is key. The honey does need to be added at trace. Sounds like things were headed downhill already and the honey was just the final straw at that point. I would make sure the lye/water mixture has cooled sufficiently (patience patience–so hard when you’re in soap mode! : ) then definitely use frozen milk, omitting the honey at least until the milk-only version wants to behave, then once that issue is squared away, trying a little honey in a small batch.

Working on it right now! This is SO addictive. I already had my milk in the freezer. I also turned down my crock pot a hair. I think it’s gonna work this time. My 9 mo. old decides to get fussy at this time. Geesh! By the way, your site is awesome.

Well, it’s in the mold! I have a confession. I snuck about an ounce of honey in it at thick trace a little bit at a time. I wasn’t brave enough to add more. Anyway, when it was done, I blopped it into the mold. I tested a cooled blob as usual, and oh, what lather! It smells nutty, and such a nice color! Can’t wait to make some more and add some yummy scents. Thanks! Gotta make new labels now.

when doing HP soap in the crockpot you have to let it bubble up like it did and fold into itself 2 times. After the 1st time scrap it down and stir it then let it bubble up and fold into itself one more time. Stir it…it should be the consistency of weird looking vasaline then add FO, EO..any other additives. Stir and then it is ready for the mold.

I have been making CP soap for a couple of years. I tried HP today and oh boy did I have a huge mess! My brother & I could not stop laughing at the way it was growing out of the crockpot!!! We still had enough, ok more then enough to make an 8# loaf of soap! It smells so wonderful and I am so excited that I don’t have to wait 3 to 4 weeks for it to cure! Thanks for the great info! We have all of our CP on our website http://www.threewolftrading.bigcartel.com and soon we will have the HP!

Was there a post on this blog about using a slow cooker to rebatch soap? Not necessarily in such a way as to fix a problem (like too much lye or whatnot), but just to be able to add delicate ingredients (flower petals, essential oils) that would be mostly fried by the initial chemical reaction? I thought there was but now I can’t find it. Thank you!

Where would I find the actual recipe for the Oatmeal & Honey Castile soap that you used in the crockpot tutorial? For some reason I can’t find it listed here, but I want to make sure that I have the right amounts before jumping in. Thank you for your detailed instructions!

I think I know what went wrong with the setting to begin with, I have watched a lot of different HP soap videos and in many of them they let it bubble over 2 or 3 times until it’s thick like mashed potatoes. Other than that I love you steps best of all I’ve seen. Could you share a recipe? Thanks, Jenn

I just ordered the lye for this project. Next is to get the castor oil. I’ll have to make a box of some kind. Also, I have a soap stamp I got made in Canada. You press it into the soap. At what point could I do this? Will the soap be soft enough to do that after cutting it into slices? Thanks. Sure looking forward to this.

If your HP wasn’t a thick glop, it hadn’t cooked long enough. It takes quite awhile and just be thick like cottage cheese. Actually a bit thicker. It won’t pour and has to be spooned into the mold and then pressed down firmly or you’ll have air pockets. I would like to know what your recipe is for CP, that you think this is milder than your CP is. What I find with HP is that you are really cooking out most of the benefits. HP should really cure for the same amount of time as CP, even though there are those saying it doesn’t. Aged soap is a better product. I saw a seller that claimed that because they use the HP method there soap is fresh. Made me laugh! A long lasting mild bar comes with age, there is just no way around it. I grew up making soap on our family farm, many moons ago and have been making soap for over 20 years (not including the time growing up). 🙂

Oh, I forgot! When using milk, use a frozen slush of milk and the key is to very slowing add your lye, only a little at a time. Constantly watching your temp, if it gets to hot you scorch the milk. Then instead of a golden beautiful color from goat milk, you will get a brown.

When do you turn on the crock pot?
I have been blending the oils and lye for twenty minutes and can’t get it to trace, so finally I turned on the crock pot to cook…I’m thinking maybe you cook while you are blending yours?
I had a really hard time with cp getting it to trace as well…though the lye calculator and I agree on the recipe.
I really enjoy your blog!
Thanks

Hi, I have made many batches of soap with no issues. Right now I am trying a new recipe that is a bit different and used soy oil. The soap has traced but will not go into that next step, in fact the oil is separating a bit. I know that the lye is still very strong. It’s been on low in the crock pot for 4 hours. Is there any way to save this?
I never made CP soap before…can I put this in a mold and let it cure for 4 weeks?
Really don’t want to waste the batch. Thanks!

I made this for the first time today and I had white foam on the bottom and sides. After an hour I still didnt have separation phase. I used a recipe with 80% olive oil, 20% coconut oil and lye/water using the lye calculator. I got a lot of soap flakes also. What did I do wrong?

deborah–I am an admitted newbie in terms of hot process. You may have done nothing wrong and merely caught the soap fairies on a day when they were in the mood for mischief. Try the experts over at latherings.com and they will probably have some intelligent advice (as opposed to mine)!

Love the tutorial!! I’ve been making hp crock-pot soap for years and won’t use any other soap. I used to use the double boiler and double batch the soap. Now I think cp-hp soap is easier and use different additives before molding.

Hi. I am just after hot processing a soap with high olive oil content. I cooked it for nearly 1 hour before moulding because it was very oily. I have moulded it and cut it and it seems to have ‘dried’ some. I think I will let it sit for a few weeks and see if it cures out. I checked my lye content and it was correct. What could have happened?
I love your website.

Val–Thank you! I wish I could help, but there are so many variables it could be. I’ve been thinking, lately, about news reports that say a lot of the olive oil sold really isn’t what it says it is, so there’s another variable to think about! Maybe it will reabsorb with time. Fingers crossed!

It sounds like she did the same thing I did. Overcooked because I wasn’t getting that jelled look. I did a rebatch (put all back in crockpot and added some water) once it was all melted and clearish, I quickly repoured into the mold and didn’t mess around with it. It came out perfectly! When I sliced it, it was like cheese and didn’t crumble like my first attempt. I think there is a tendency to overcook the first time to make sure the lye has neutralized.

Sherry Giannini–Sorry, there is no way to make this without lye. If you want to “make” soap without lye, you will have to go the melt-and-pour route. That is a product which is basically bulk soap which you can melt and then to which you can add smells and other additives and then pour it into molds, sold in hobby stores and online soaping supply stores.

This recipe has far too much water for the amount of lye and oils. No wonder it takes so long to cure! Given that amount of lye I would have only used 9 oz water. HP recipes and CP recipes should different in liquid…most lye calculators don’t take that into account, hence I don’t use them!.

Could I use a different oil such as coconut, almond or argan oils. And what exactly is ” melt and pour route” I was thinking the same thing as the other person. I thought lye wasn’t good for your skin?

Melt and Pour is a glycerin soap that artisans melt first, then pour into various molds for use. Sometimes they add scents, colors, oils, etc…but the M&P product is ready for use when they get it. Cold process or hot process soap making involves taking pure fats, adding lye, allowing for the chemical process of saponification, and voila you have soap. SOAP of any sort has lye in it, that is what makes it soap. And yes, too much lye, lye that hasn’t completed the chemical process, that can hurt your skin (burn)…proper soap making and time makes sure there is no lye left in the batch.

Desiree–You can use different oils, just put them in a lye calculator like this one: MMS to get your adjusted lye and water amounts. Lye is certainly caustic on it’s own, but once it is blended with water and mixed into oils in the right proportions and allowed to cure, it is, simply, just soap, and is what we’ve always known and experienced as soap. It’s the only way to do it!

I made this soap several months ago. While it was very easy and straightforward, my skin did not like it. I gave lots of it away, and everyone I gave it to LOVED it. Fast forward about 2 or 3 months…I was out of soap. I grabbed a bar, and lo and behold, it was fine. Lesson learned: if it isn’t working, let it age. I will be making another batch to age for a while this week.

Deanna I have enjoyed reading your post!! I have dibbled in soap making off and on for 3 years. I enjoy the process. I also own a small business (Global Spice Exchange) specializing in natural products for artisans who make their own products. I am contemplating adding a blog to my website and would love your permission to include this post for novice soap makers. I invite you to browse my site at your leisure if needed to base your decision. http://www.globalspiceexchange.com/#

Nicole–Thank you. Sure, we welcome folks to put brief intros with a link to one of our posts on their site. Obviously the post in its entirety with no attribution isn’t cool, which I’m sure you know (but you wouldn’t believe what happens sometimes!) 🙂

Hi, I need help! I made a triple batch of hot process soap yesterday. I have used the same recipe with success prior but holy cow something has gone horribly wrong. I looks like curdled cheese and it has oil sitting on top. What did I do? Can it be fixed???

Sorry but Castille is ONLY olive oil, please stop spreading misinformation so the real soapers out there will no longer have to keep straightening out this crap. Pure oil soaps are NOT Castille, 100% olive ONLY as this is the recipe originally from Castille.

I am excited to add honey to my crock pot soap. Great job! You can check if it is done by touching the soap to the tip of your tongue. If it tingles it is not ready. 🙂 mine usually takes 14 hourish. I have left it for 24 out of laziness and it was fine. Seemed to lather better. COuld have just been that batch. Who knows. Where does everyone buy their lye? It is expensive here and I have to search it out at farm stores. I am in Columbus Ga.

Hey Gals–
Been making soap for 17 years. Been earning my living for 15 years with my soaps.

That separation phase only happens every once in a great while. The soap is not done at this point, it is only starting to cook. If this happens, you should put the stick blender back in and get it back to trace. (BTW and plastic things that come into contact with the lye are contaminated and should not be used for food again. The soap will rise up several times–the process takes about 45 minutes for an average size batch. When the soap is done cooking, it looks like really thick mashed Yukon Gold potatoes, it starts sticking to the sides and it quits rising up out of the crock.

The soap at the point you showed first going into the mold is not soap at all–just a blend of oils and lye…in other words…not safe to use and it will burn and scar you if you are not careful. If you cook to the point that the soap is “done”, you then let it cool down to about 140 degrees and then add you scent and other additives. I let mine cure about two weeks to harden up. But once it is done, you can take a small dot of the soap out and try it. Castile soaps (100% olive oil) do not lather, they have a small foamy lather and are VERY moisturizing. On my skin that means almost slimy. But in this recipe with the addition of the castor you should have a bit of lather. Also, while the bar of soap is very hard, that does not mean it won’t melt away if you leave it sit in a puddle of water.

If any of you have other questions on soapmaking, you can reach my email link on my website. Great pictures and blog–just wanted to make sure you end up with a safe product that won’t remove three layers of skin or blind you.

If you could give me the measurements that would be great . And also can you use other types of molds? And I didn’t see any of the ways to make it in the cold process . Would like to see them too. Thank you for your time

Sharon, immersion blender is the only way to efficiently make soap using lye; saponification by hand just takes far too long. I have been using the same immersion blender (for soap ONLY) for almost 8 years now, it is going strong.